It was the second time Syrian forces have violently dispersed a small protest this week. Syrians have tried to stage demonstrations inspired by those sweeping the Arab world, but intimidation and other factors have squelched the gatherings in a country that routinely jails critics of the regime.

The protesters had gathered outside the Interior Ministry calling for the release of political prisoners.

"These protests have been real acts of bravery in a country known for its intolerance of dissent," said Philip Luther, Amnesty International's deputy director for the Middle East and North Africa.

One man being treated for a serious head wound was reportedly arrested at a hospital and also taken to an unknown location, Amnesty said.

Eight Syrian human rights groups signed a statement Wednesday denouncing the crackdown. The statement said six activists were among those detained.

In Washington, State Department spokesman Mark Toney expressed concern about reported casualties. "People everywhere, including the Syrian people, have the universal right to peacefully assemble and freely express their opinions," Toner said.

On Tuesday, witnesses said Syrian government supporters broke up a small pro-democracy demonstration in the capital by punching and attacking the protesters. They were demanding an end to emergency laws that give authorities a free hand to jail activists.

Syria, a predominantly Sunni country ruled by minority Alawites, has been spared the wave of uprisings in the Middle East. Part of the reason is that the protesters know there will be a swift crackdown.

But some observers note that President Bashar Assad's popular anti-Israel policies have united the country behind him to a certain degree.